/Engine/Plugins/Runtime/MassGameplay/Source/MassRepresentation/Public/MassInstancedStaticMeshComponent.h
Add multiple instances to this component. The newly added instances are associated with Ids as indicated by InstanceIds.
void AddInstancesWithIds ( TConstArrayView< int32 > InstanceIds, TConstArrayView< FTransform > InstanceTransforms, int32 InNumCustomDataFloats, TConstArrayView< float > CustomFloatData, bool bWorldSpace, [TArray](API\Runtime\Core\Containers\TArray)< int32 > * OutAddedIndices )